In the production of pigmented paints, pigments are typically added to the paint as a component of a pigment paste which, in addition to pigment, also typically includes an organic resin. Pigments are commercially available in presscake or dry powder form and are made up of primary particles in the submicron size range. Primary pigment particles exist in various forms, such as aggregates, agglomerates, flocculates or combinations of these forms. To maximize the color properties of a pigment, such as strength, transparency, gloss, rheology and lightfastness, the pigment needs to be dispersed in a carrier medium in as finely divided a form as possible, preferably into primary pigment particles.
Dispersion of a pigment in a pigment paste is typically accomplished by subjecting a mixture of pigment and an organic resin, known as a grind vehicle, to a high shear and high stress process known as grinding or milling. The process of dispersion consists of (1) wetting the pigment surface with the resin, (2) deaggregating and deagglomerating pigment particles, and (3) stabilizing the dispersed pigment particles from flocculating upon standing or subsequent paint formulation.
Pigment grind vehicles have several important characteristics. Since many grinding processes are time intensive, the ability of a grind vehicle to disperse a pigment quickly to a given particle size is important.
A second important characteristic of a pigment grind vehicle is the ability to impart a low viscosity to a pigment paste at a given degree of grinding and to maintain low viscosity over time. When a pigment paste has good viscosity properties, higher resin solids paints can be prepared because the viscosity component of the paint due to the pigment paste will be less.
Another important characteristic of a pigment grind vehicle is the ability to achieve good color properties, such as those identified above, for a given pigment. Such properties principally relate to the degree of pigment dispersion which can be achieved by a grind vehicle.
While many commercial pigment grinding vehicles are available on the market, there exists a continuing need for pigment grinding vehicles which are improved in one or more of the above-described characteristics.